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The widespread use of herbicides in cropping systems has led to the evolution of resistance in major weeds. The resultant loss of herbicide efficacy is compounded by a lack of new herbicide sites of action, driving demand for alternative weed control technologies. While there are many alternative methods for control, identifying the most appropriate method to pursue for commercial development has been hampered by the inability to compare techniques in a fair and equitable manner. Given that all currently available and alternative weed control methods share an intrinsic energy consumption, the aim of this review was to compare methods based on energy consumption. Energy consumption was compared for chemical, mechanical, and thermal weed control technologies when applied as broadcast (whole-field) and site-specific treatments. Tillage systems, such as flex-tine harrow (4.2 to 5.5 MJ ha−1), sweep cultivator (13 to 14 MJ ha−1), and rotary hoe (12 to 17 MJ ha−1) consumed the least energy of broadcast weed control treatments. Thermal-based approaches, including flaming (1,008 to 4,334 MJ ha−1) and infrared (2,000 to 3,887 MJ ha−1), are more appropriate for use in conservation cropping systems; however, their energy requirements are 100- to 1,000-fold greater than those of tillage treatments. The site-specific application of weed control treatments to control 2-leaf-stage broadleaf weeds at a density of 5 plants m−2 reduced energy consumption of herbicidal, thermal, and mechanical treatments by 97%, 99%, and 97%, respectively. Significantly, this site-specific approach resulted in similar energy requirements for current and alternative technologies (e.g., electrocution [15 to 19 MJ ha−1], laser pyrolysis [15 to 249 MJ ha−1], hoeing [17 MJ ha−1], and herbicides [15 MJ ha−1]). Using similar energy sources, a standardized energy comparison provides an opportunity for estimation of weed control costs, suggesting site-specific weed management is critical in the economically realistic implementation of alternative technologies.
Chemical analysis by the X-ray fluorescence microprobe technique offers potential means for the determination of compositional differences arising from the segregation of elements during the solidification of metals. The dimensional scale of the probe is expected to be suitable for the study of macro segregation and, in coarse-grained cast materials, of interdendritic micro segregation.
This paper describes preliminary work carried out to establish analytical sensitivity in respect of some minor constituents present in homogeneous steel samples of known composition. The significance of the results is discussed in relation to the problems of segregation in steel, and it is concluded that the Siemens Kristalloflex IV equipment needs to be adapted for fully focusing operation to achieve the sensitivity required for this work. Details are given of the work so far undertaken in this direction.
Objectives: Prior research has identified numerous genetic (including sex), education, health, and lifestyle factors that predict cognitive decline. Traditional model selection approaches (e.g., backward or stepwise selection) attempt to find one model that best fits the observed data, risking interpretations that only the selected predictors are important. In reality, several predictor combinations may fit similarly well but result in different conclusions (e.g., about size and significance of parameter estimates). In this study, we describe an alternative method, Information-Theoretic (IT) model averaging, and apply it to characterize a set of complex interactions in a longitudinal study on cognitive decline. Methods: Here, we used longitudinal cognitive data from 1256 late–middle aged adults from the Wisconsin Registry for Alzheimer’s Prevention study to examine the effects of sex, apolipoprotein E (APOE) ɛ4 allele (non-modifiable factors), and literacy achievement (modifiable) on cognitive decline. For each outcome, we applied IT model averaging to a set of models with different combinations of interactions among sex, APOE, literacy, and age. Results: For a list-learning test, model-averaged results showed better performance for women versus men, with faster decline among men; increased literacy was associated with better performance, particularly among men. APOE had less of an association with cognitive performance in this age range (∼40–70 years). Conclusions: These results illustrate the utility of the IT approach and point to literacy as a potential modifier of cognitive decline. Whether the protective effect of literacy is due to educational attainment or intrinsic verbal intellectual ability is the topic of ongoing work. (JINS, 2019, 25, 119–133)
Laser-based compact MeV X-ray sources are useful for a variety of applications such as radiography and active interrogation of nuclear materials. MeV X rays are typically generated by impinging the intense laser onto ~mm-thick high-Z foil. Here, we have characterized such a MeV X-ray source from 120 TW (80 J, 650 fs) laser interaction with a 1 mm-thick tantalum foil. Our measurements show X-ray temperature of 2.5 MeV, flux of 3 × 1012 photons/sr/shot, beam divergence of ~0.1 sr, conversion efficiency of ~1%, that is, ~1 J of MeV X rays out of 80 J incident laser, and source size of 80 m. Our measurement also shows that MeV X-ray yield and temperature is largely insensitive to nanosecond laser contrasts up to 10−5. Also, preliminary measurements of similar MeV X-ray source using a double-foil scheme, where the laser-driven hot electrons from a thin foil undergoing relativistic transparency impinging onto a second high-Z converter foil separated by 50–400 m, show MeV X-ray yield more than an order of magnitude lower compared with the single-foil results.
Objectives: A major challenge in cognitive aging is differentiating preclinical disease-related cognitive decline from changes associated with normal aging. Neuropsychological test authors typically publish single time-point norms, referred to here as unconditional reference values. However, detecting significant change requires longitudinal, or conditional reference values, created by modeling cognition as a function of prior performance. Our objectives were to create, depict, and examine preliminary validity of unconditional and conditional reference values for ages 40–75 years on neuropsychological tests. Method: We used quantile regression to create growth-curve–like models of performance on tests of memory and executive function using participants from the Wisconsin Registry for Alzheimer’s Prevention. Unconditional and conditional models accounted for age, sex, education, and verbal ability/literacy; conditional models also included past performance on and number of prior exposures to the test. Models were then used to estimate individuals’ unconditional and conditional percentile ranks for each test. We examined how low performance on each test (operationalized as <7th percentile) related to consensus-conference–determined cognitive statuses and subjective impairment. Results: Participants with low performance were more likely to receive an abnormal cognitive diagnosis at the current visit (but not later visits). Low performance was also linked to subjective and informant reports of worsening memory function. Conclusions: The percentile-based methods and single-test results described here show potential for detecting troublesome within-person cognitive change. Development of reference values for additional cognitive measures, investigation of alternative thresholds for abnormality (including multi-test criteria), and validation in samples with more clinical endpoints are needed. (JINS, 2019, 25, 1–14)
Chondrules contain ferromagnetic minerals that may retain a record of the magnetic field environments in which they cooled. Paleomagnetic experiments on separated chondrules can potentially reveal the presence of remanent magnetization from the time of chondrule formation. The existence of such a magnetization places quantitative bounds on the frequency of interchondrule collisions, while the intensity of magnetization may be used to infer the strength of nebular magnetic fields and thereby constrain the mechanism of chondrule formation. Recent advances in laboratory instrumentation and techniques have permitted the isolation of nebular remanent magnetization in chondrules, providing the potential basis to probe the formation environments of chondrules from a range of chondrite classes.
Knowledge of the effects of burial depth and burial duration on seed viability and, consequently, seedbank persistence of Palmer amaranth (Amaranthus palmeri S. Watson) and waterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer] ecotypes can be used for the development of efficient weed management programs. This is of particular interest, given the great fecundity of both species and, consequently, their high seedbank replenishment potential. Seeds of both species collected from five different locations across the United States were investigated in seven states (sites) with different soil and climatic conditions. Seeds were placed at two depths (0 and 15 cm) for 3 yr. Each year, seeds were retrieved, and seed damage (shrunken, malformed, or broken) plus losses (deteriorated and futile germination) and viability were evaluated. Greater seed damage plus loss averaged across seed origin, burial depth, and year was recorded for lots tested at Illinois (51.3% and 51.8%) followed by Tennessee (40.5% and 45.1%) and Missouri (39.2% and 42%) for A. palmeri and A. tuberculatus, respectively. The site differences for seed persistence were probably due to higher volumetric water content at these sites. Rates of seed demise were directly proportional to burial depth (α=0.001), whereas the percentage of viable seeds recovered after 36 mo on the soil surface ranged from 4.1% to 4.3% compared with 5% to 5.3% at the 15-cm depth for A. palmeri and A. tuberculatus, respectively. Seed viability loss was greater in the seeds placed on the soil surface compared with the buried seeds. The greatest influences on seed viability were burial conditions and time and site-specific soil conditions, more so than geographical location. Thus, management of these weed species should focus on reducing seed shattering, enhancing seed removal from the soil surface, or adjusting tillage systems.
J. F. Cooper, NASA Goddard Space Flight Center Greenbelt, Maryland, USA,
R. E. Johnson, University of Virginia Charlottesville, Virginia, USA,
P. Kollmann, Johns Hopkins University Applied Physics Laboratory Laurel, Maryland, USA,
E. Roussos, Max Planck Institute for Solar System Studies Göttingen, GERMANY,
E. C. Sittler, NASA Goddard Space Flight Center Greenbelt, Maryland, USA
Ring systems around magnetized planets are expected to have varied interactions with the magnetic fields, hot plasma, and energetic particles of the associated magnetospheres. In our solar system all the giant planets, Jupiter to Neptune, have magnetospheres with embedded rings. Each ring system and its associated moons have strong interactions with their radiation environments (the most intense of which is at Jupiter). Such interactions both erode diffuse rings (such as the E ring of Saturn) and supply plasma and energetic particles to the magnetosphere and its radiation belts. Compositional and structural measurements of rings are enabled by these interactions, such as the information obtained by detection of the secondary neutron and gamma-ray emissions produced by galactic cosmic ray (GCR) interactions with the rings. It is also notable that Earth has both a magnetosphere with radiation belts, and an artificial ring system of satellites and debris, that continuously interact. Konradi (1988) even projected that the high energy trapped protons of the inner Van Allen Belt should now be experiencing significant depletion by this interaction, and we will later discuss the possible evidence for this. Magnetized exoplanets with rings would have similar interactions.
The ring systems of Jupiter and Saturn have been explored by multiple spacecraft. The Jovian ring environment was first explored in situ in 1974 by Pioneer 11, which subsequently flew under Saturn's main rings in 1979. After passing through the Saturn ring plane near the G ring in 1981, Voyager 2 encountered Uranus in 1986 and then Neptune in 1989, but in neither case were the rings and arcs of these two ice giant planets traversed. The Galileo Probe passed across the Jovian ring in December 1995 en route to the first direct penetration into Jupiter's atmosphere. The Cassini Orbiter crossed over the Saturn A and B rings in mid-2004 (Figure 14.1) as part of the Saturn Orbital Insertion (SOI). Cassini will again traverse the main rings during its Grand Finale orbit phase many times, crossing the ring plane just inwards of the D ring, prior to final atmospheric entry in 2017. With the exception of the Cassini Plasma Spectrometer (CAPS) instrument, turned off in 2012 due to electrical problems, Cassini will continue to operate through the final observations.
Measurements of snow accumulation are critical for reliable prediction of future ice mass loss and hence projections of sea level change. However, there are currently very few published in situ measurements of snow accumulation in the Pine Island–Thwaites glacier catchment of the Amundsen Sea Embayment, and none from low elevation sites west of 100.77° longitude. Here measurements of snow accumulation over an 11 month period in 2016 are reported for six sites in the Pine Island–Thwaites glacier catchment. The average accumulation rates of 0.10±0.01 to 1.26±0.22 m w.e. yr-1 are comparable with those derived from airborne radar for the period 1985–2009, suggesting very high rates of snowfall, particularly in the vicinity of the grounding line.
Competition from weeds is one of the major biophysical constraints to rice (Oryza spp.) production in sub-Saharan Africa. Smallholder rice farmers require efficient, affordable and labour-saving weed management technologies. Mechanical weeders have shown to fit this profile. Several mechanical weeder types exist but little is known about locally specific differences in performance and farmer preference between these types. Three to six different weeder types were evaluated at 10 different sites across seven countries – i.e., Benin, Burkina Faso, Côte d'Ivoire, Ghana, Nigeria, Rwanda and Togo. A total of 310 farmers (173 male, 137 female) tested the weeders, scored them for their preference, and compared them with their own weed management practices. In a follow-up study, 186 farmers from Benin and Nigeria received the ring hoe, which was the most preferred in these two countries, to use it during the entire crop growing season. Farmers were surveyed on their experiences. The probability of the ring hoe having the highest score among the tested weeders was 71%. The probability of farmers’ preference of the ring hoe over their usual practices – i.e., herbicide, traditional hoe and hand weeding – was 52, 95 and 91%, respectively. The preference of this weeder was not related to gender, years of experience with rice cultivation, rice field size, weed infestation level, water status or soil texture. In the follow-up study, 80% of farmers who used the ring hoe indicated that weeding time was reduced by at least 31%. Of the farmers testing the ring hoe in the follow-up study, 35% used it also for other crops such as vegetables, maize, sorghum, cassava and millet. These results suggest that the ring hoe offers a gender-neutral solution for reducing labour for weeding in rice as well as other crops and that it is compatible with a wide range of environments. The implications of our findings and challenges for out-scaling of mechanical weeders are discussed.
Leptin is a signalling factor involved in the regulation of body weight and is synthesised predominantly by adipocytes. In humans, there is a positive correlation between plasma concentration of leptin and body mass index (kg/m_a3) and subcutaneous fat (Considine et al., 1996; Lonnqvist et al., 1995). In vitro adipocytes obtained from women secrete more leptin than those of men (Casabeill et al., 1998). Furthermore, testosterone inhibits the expression of the leptin gene in the rat (Wu-Peng et al., 1999). The aim of this study was to examine whether gender, age and body conformation influenced plasma leptin and thyroid hormone concentrations in the horse. Materials and method Pre-slaughter body weight and height were recorded in a random group of mares (n=5), geldings (castrated males: n=7) and stallions (n=3) destined for human consumption. Their age was estimated by dental examination. Immediately post-mortem, a jugular vein blood sample was collected into a heparinised tube, which was centrifuged at 2500 rpm for 10 minutes. Plasma was stored in liquid nitrogen until analysed for plasma concentrations of leptin and thyroid hormones using human ELISA (DRG Instruments) and RIA kits (ICN Pharmaceuticals Ltd), respectively. Statistical differences between groups were assessed using General Linear Model, Analysis of Variance. Regression analysis was used to determine whether plasma leptin concentration was related to body conformation and age.
The Deep Ice Sheet Coring (DISC) drill developed by Ice Coring and Drilling Services under contract with the US National Science Foundation is an electromechanical ice-drill system designed to take 122mm ice cores to depths of 4000 m. The new drill system was field-tested near Summit camp in central Greenland during the spring/summer of 2006. Testing was conducted to verify the performance of the DISC drill system and its individual components and to determine the modifications required prior to the system’s planned deployment for coring at the WAIS Divide site in Antarctica in the following year. The experiments, results and the drill crew’s experiences with the DISC drill during testing are described and discussed.
The Southern Hemisphere VLBI Experiment (or SHEVE) was a joint US-Australian-South African venture with both astronomy and geodesy goals. The principle astronomy goal was to make models or maps of the following sources: at 2.3 GHz (with six antennas and 9 usable baselines) – Centaurus A (the nearest active galaxy), Circinus X-1 (a flaring binary), the VELA pulsar, and 26 other active galactic nuclei and quasars; at 8.4 GHz (only one baseline) – Centaurus A and the galactic center.
Six radio telescopes were operated as the first southern hemisphere VLBI array in April and May 1982. Observations were made at 2.3 and 8.4 Ghz. This array produced VLBI images of 28 southern hemisphere radio sources, high accuracy VLBI geodesy between southern hemisphere sites, and subarcsecond radio astrometry of celestial sources south of declination −45 degrees. This paper discusses only the astrophysical aspects of the experiment.
This study uses an experiment where ferry passengers are sold hotel room “views” to evaluate the impact of wind turbines views on tourists’ vacation experience. Participants purchase a chance for a weekend hotel stay. Information about the hotel rooms was limited to the quality of the hotel and its distance from a large wind turbine, as well as whether or not a particular room would have a view of the turbine. While there was generally a negative effect of turbine views, this did not hold across all participants, and did not seem to be effected by distance or hotel quality.
We present our models of the effect of binaries on high-resolution spectroscopic surveys. We want to determine how many binary stars will be observed, whether unresolved binaries will contaminate measurements of chemical abundances, and how we can use spectroscopic surveys to better constrain the population of binary stars in the Galaxy. Using a rapid binary-evolution algorithm that enables modelling of the most complex binary systems we generate a series of large binary populations in the Galactic disc and evaluate the results. As a first application we use our model to study the binary fraction in APOGEE giants. We find tentative evidence for a change in binary fraction with metallicity.
The Numeniini is a tribe of 13 wader species (Scolopacidae, Charadriiformes) of which seven are Near Threatened or globally threatened, including two Critically Endangered. To help inform conservation management and policy responses, we present the results of an expert assessment of the threats that members of this taxonomic group face across migratory flyways. Most threats are increasing in intensity, particularly in non-breeding areas, where habitat loss resulting from residential and commercial development, aquaculture, mining, transport, disturbance, problematic invasive species, pollution and climate change were regarded as having the greatest detrimental impact. Fewer threats (mining, disturbance, problematic native species and climate change) were identified as widely affecting breeding areas. Numeniini populations face the greatest number of non-breeding threats in the East Asian-Australasian Flyway, especially those associated with coastal reclamation; related threats were also identified across the Central and Atlantic Americas, and East Atlantic flyways. Threats on the breeding grounds were greatest in Central and Atlantic Americas, East Atlantic and West Asian flyways. Three priority actions were associated with monitoring and research: to monitor breeding population trends (which for species breeding in remote areas may best be achieved through surveys at key non-breeding sites), to deploy tracking technologies to identify migratory connectivity, and to monitor land-cover change across breeding and non-breeding areas. Two priority actions were focused on conservation and policy responses: to identify and effectively protect key non-breeding sites across all flyways (particularly in the East Asian- Australasian Flyway), and to implement successful conservation interventions at a sufficient scale across human-dominated landscapes for species’ recovery to be achieved. If implemented urgently, these measures in combination have the potential to alter the current population declines of many Numeniini species and provide a template for the conservation of other groups of threatened species.
Objectives: Intraindividual cognitive variability (IICV) has been shown to differentiate between groups with normal cognition, mild cognitive impairment (MCI), and dementia. This study examined whether baseline IICV predicted subsequent mild to moderate cognitive impairment in a cognitively normal baseline sample. Methods: Participants with 4 waves of cognitive assessment were drawn from the Wisconsin Registry for Alzheimer’s Prevention (WRAP; n=684; 53.6(6.6) baseline age; 9.1(1.0) years follow-up; 70% female; 74.6% parental history of Alzheimer’s disease). The primary outcome was Wave 4 cognitive status (“cognitively normal” vs. “impaired”) determined by consensus conference; “impaired” included early MCI (n=109), clinical MCI (n=11), or dementia (n=1). Primary predictors included two IICV variables, each based on the standard deviation of a set of scores: “6 Factor IICV” and “4 Test IICV”. Each IICV variable was tested in a series of logistic regression models to determine whether IICV predicted cognitive status. In exploratory analyses, distribution-based cutoffs incorporating memory, executive function, and IICV patterns were used to create and test an MCI risk variable. Results: Results were similar for the IICV variables: higher IICV was associated with greater risk of subsequent impairment after covariate adjustment. After adjusting for memory and executive functioning scores contributing to IICV, IICV was not significant. The MCI risk variable also predicted risk of impairment. Conclusions: While IICV in middle-age predicts subsequent impairment, it is a weaker risk indicator than the memory and executive function scores contributing to its calculation. Exploratory analyses suggest potential to incorporate IICV patterns into risk assessment in clinical settings. (JINS, 2016, 22, 1016–1025)